A hopper wagon is a type of freight railway vehicle for transporting bulk commodities. Typically the bulk commodity is held in a generally box-shaped hopper wagon body that is supported by an under-frame. The underframe may be coupled to bogies so that the hopper wagon can be moved along a railway track.
The bulk commodity may be loaded into the hopper wagon body through an inlet aperture at the top of the wagon body, and may be discharged through an outlet aperture at the bottom of the wagon body. In covered hopper wagons, the inlet is provided with a cover to protect the bulk commodity held in the hopper wagon body.
The cover may comprise a simple removable sheet. However, this type of cover system must be operated manually, and has the further disadvantage that the sheet must be stored when it is not in use. Other cover systems include one or more doors that can be moved between open and closed configurations in a sliding or rotating action. Advantageously, the doors of these types of cover system remain attached to the hopper wagon body during use and may be driven to slide or rotate using an automatic, or semi-automatic, actuating system.
The doors are typically arranged as an opposing pair of door leaves that are hingedly mounted at their proximal edges on longitudinal side walls of the wagon body and rotate about substantially horizontal axes between an open configuration, in which the doors extend generally upwards away from the open top of the wagon body, and a closed configuration, in which doors extend towards each other generally across the top of the wagon body to substantially cover the inlet as their distal edges engage each other.
In automatic, or semi-automatic, systems pneumatic or hydraulic actuators are arranged to move the doors between the open and closed configurations. Each door has a pair of actuators that are typically mounted on opposed end walls of the wagon. Piston rods of the actuators act directly upon frame members of the doors.
One disadvantage of this design is that when the doors are fully open, such as during the loading of the wagon, the piston rods project above the end walls of the wagon body. As a result, the piston rods may impair access to the inlet, conflict with a loading chute and impede the loading of the bulk commodity. The piston rods may be vulnerable to damage from inadvertent contact with the loading chute and/or with the bulk commodity material itself during the loading process. Such damage, if it occurs, can be costly as the cylinder must be replaced.
Embodiments of the invention seek to provide an alternative and improved inlet closure system. Embodiments of the present invention aim to address the disadvantages of the previously considered inlet closure systems.